1. Field of the Invention
The present invention relates to a thin-film magnetic head with a magnetoresistive effect (MR) read head element, to a magnetic head assembly, to a magnetic disk drive apparatus, and to a method for manufacturing a thin-film magnetic head.
2. Description of the Related Art
As hard disk drive (HDD) apparatuses increase in capacity and reduce in size, highly sensitive thin-film magnetic heads capable of coping with higher recording density are being demanded. In order to meet this demand, characteristics of a giant magnetoresistive effect (GMR) thin-film magnetic head with a GMR read head element are being improved. On the other hand, a tunnel magnetoresistive effect (TMR) thin-film magnetic head with a TMR read head element that will provide magnetoresistivity more than twice as high as that of the GMR thin-film magnetic head has become commercially practical.
Recently, lower and upper shield layers sandwiching an MR layer in an MR read head element of such a thin-film magnetic head for supporting a high recording density are becoming thinner. As the shield thickness of the lower and upper shield layers becomes thinner with respect to the shield width, the concentration of magnetic fluxes on their end edges becomes prominent. While this tendency appears in the lower and upper shield layers formed thin by plating as well, it is especially noticeable when films of the lower and upper shield layers are deposited by sputtering and then patterned by ion milling. This is because cross-section of the layers is sharpened by ion milling regardless of the width or thickness of the end edges of the layers.
FIG. 1 illustrates a cross-section of one end edge of a lower shield layer fabricated as a thin film by using a conventional method, viewed from the air bearing surface (ABS) side of a thin-film magnetic head.
As will be understood from FIG. 1, the end edge 10a of the lower shield layer 10 appeared at the ABS if it is fabricated by a conventional manufacturing method is not vertical to the layer-lamination planes but is sloped. This slope has caused a problem that magnetic fields concentrate at the end edge 10a under the influence of external magnetic fields or magnetic fields from the write head element and the concentrated magnetic fields are applied to a magnetic medium facing the thin-film magnetic head, inducing an unwanted write to the magnetic medium. This adverse effect on a magnetic medium caused by the shape of the end edges of the lower and upper shield layers has been more noticeable in an apparatus where the write head element has a perpendicular magnetic recording structure than in that where the write head element has a horizontal or plane magnetic recording structure.
Japanese patent publication No. 2001-006121A discloses a technique for reducing the adverse effect of magnetic flux leakage from a thin-film magnetic head. According to the technique disclosed in Japanese patent publication No. 2001-006121A, the thin-film magnetic head has shunts at an end of its write head part facing a magnetic recording medium to pass leakage magnetic fluxes that may be recorded on the magnetic recording medium as write fringes through the shunts, and thus write fringes caused by the magnetic flux leakage at the recording gap can be reduced.
However, Japanese patent publication No. 2001-006121A merely discloses to guide leakage magnetic fluxes from the recording gap of the write head part to the shunts provided on both sides of the recording gap, but does not disclose leakage magnetic flux produced from a read head part of the thin-film magnetic head. Thus, the position of leakage magnetic fluxes disclosed in Japanese patent publication No. 2001-006121A differs completely from that of the present invention. In addition, the technique disclosed in Japanese patent publication No. 2001-006121A does not reduce flux leakage itself. Therefore, the known technique cannot be used for reducing magnetic flux leakage at the edges of the lower and upper shield layers of an MR read head element. In particular, it is difficult to provide the shunts described in Japanese patent publication No. 2001-006121A in the vicinity of the lower and upper shield layers of an MR read head element, due to limitations of space. Even if such shunts can be provided, it is difficult to reduce magnetic flux leakage at the edges of the lower and upper shield layers by the shunts.